Power transformers are the most important components of an electrical grid. The transformers differ by their cooling systems. Hence there are dry-type transformers and oil immersed transformers
Most of the transformers in service are oil immersed. Their tank with active part is filled with oil. The oil removes heat from hot parts and increases dielectric strength of insulation. Transformers with an air cooling system are called dry-type transformers. Usually they have a small capacity of 1000-1600 kVA and a voltage of 10-15 kV. Also there are transformers with mixed oil-water cooling systems with forced oil circulation.
Oil immersed transformer structure
The basic elements of an oil immersed and dry-type transformer are the same and consist of magnetic circuit, windings and bushings. A magnetic circuit is a core that provides a path for magnetic flow. Windings create a magnetic field and consist of a conductor coil, wrapped around the core, insulated with pressboard barriers and screens. Thickness of the windings insulation increases with voltage level. Bushings connect transformer windings to a substation.
A characteristic feature of an oil immersed transformer is a surge tank. It simplifies the operation by monitoring the oil level in a tank.
Oil is the basis of the insulation system of power transformers
Oil is also an important part of a transformer. It is used as a heat transfer medium, as insulation of active parts and a dielectric.
During operation, transformer oil is under the influence of a number of negative factors: high temperature, oxygen, water, high voltage, etc. which deteriorate oil properties. Contaminated oil becomes dangerous for the equipment.
GlobeCore designed oil purification and regeneration plants that can connect directly to transformers. Since changing of insulating oil in many cases does not provide the desired result, as many aging products remain in a tank. These contaminants get into new oil, and intensify the aging process. A CMM-R unit form GlobeCore is able to solve this problem. An important feature of this unit is its ability to process insulating oil in energized or de-energized transformers. The unit connects directly to a transformer and circulates oil in a closed loop with an oil flow washing away all aging products. The oil completely restores all necessary properties and parameters to the normalized values, and the transformer can continue to operate in the normal mode.
Regular regeneration of oils can significantly prolong their service life, improve reliability of transformers and saves costs on purchase and disposal of oil.